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Cisco 3660 ISDN BRI Problem

I have a Cisco 3660 rtr with d following IOS ver:

IOS (tm) 3600 Software (C3660-IS-M), Version 12.0(7)XK1, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)

I have a NM 4B-S/T ISDN module with 4 128K ISDN lines connected. I have set d encapsulation to ppp & d isdn switch type is basic-net3.

The problem I face is tht whenever I do a self dial 2 chk my ISDN d call last 4 only 5-10 secs & then drops immediately. At this point of time if I chk d ISDN status it shows Layer 1 as Active & Layer 2 as Not Activated. After sometime d Layer 2 automatically bcums MULTI_FRAME_ESTD. The voice calls & Video conferencing works perfectly with d same line. My service provider has also done a BERT test which gives error-free result. I will also give my ISDN config below:-

interface BRI2/0

description ***** ISDN Backup No. 0222490**** *****

no ip address

no ip directed-broadcast

encapsulation ppp

dialer pool-member 1

isdn switch-type basic-net3

no cdp enable

ppp authentication chap


interface Dialer0

description ***** ISDN Backup to Fort Office *****

ip unnumbered Serial1/0

no ip directed-broadcast

encapsulation ppp

dialer remote-name XY-XYZ02-RTR01

dialer pool 1

dialer idle-timeout 1800

dialer string 226*****

dialer-group 1

no cdp enable

ppp authentication chap


Due to this problem I have been unable to efficiently use d ISDN as a backup for my LL. I have also configured a syslog Server for the same rtr. Though my same syslog config works with my other rtrs & I do get syslog msgs on my Server...4 this rtr it doesnt work.

Plz let me know if there is a configuration mistake or there is a known bug with this IOS version. Thnx in advance


Re: Cisco 3660 ISDN BRI Problem

Hi Frined,

I know its a basic stuff but just make sure that there is no mismatch of chap password configuration.

I experienced the same problem and later realised it was password mismatch on the remote end.

Configuration looks fine.



VIP Purple

Re: Cisco 3660 ISDN BRI Problem


since you are using CHAP, make sure that the username and passwords on both your routers do not have typos, and that the passwords match, that is, on the router of which you have shown the partial configuration, you need a line like this:

username XY-XYZ02-RTR01 password XXXXXX

The username is case-sensitive, on the other side you need the same.

Also, and you probably have this configured, make sure that the 'dialer-list 1 protocol ip permit' statement is configured on your router.

You might want to post the full configurations of both routers, maybe there is something that can be spotted...)



New Member

Re: Cisco 3660 ISDN BRI Problem

Thnx both of u...I'll definitely chk abt the chap settings & will also try 2 post d entire config. But tell me 1 thing...if my chap configuration is incorrect then it will get disconnected from ISDN..accepted; but y will d physical status..Layer 2 status change from MULTI_FRAME_ESTD to NOT ACTIVATED. Also leave apart remote side dialing in, its happening with self dial itself. Anways I reply 1ce again within 2 hrs.

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